Various technical references are referred to herein using numerals in square brackets, [ ]. A complete citation for each of these references is provided at the end of the application.
In order to conserve battery energy of user equipment (UE) (user terminal or mobile station), a UE that has not received or performed transmissions for an extended period of time is quite likely to be placed in an RRC_IDLE state and is woken up by a paging message if there is traffic, an Earthquake Tsunami Warning System (ETWS) message, and/or updated broadcast system information to be delivered to or received by that UE. It is expected that UEs will likely spend a majority of their time in this RRC_IDLE state.
A UE may also be placed in a different type of “idle” mode while remaining in the RRC_CONNECTED state. This mode is referred to as DRX (Discontinuous Reception), and allows a UE to “sleep” for a certain portion of a configured DRX cycle. During this sleep portion of the cycle, the UE is not expected to receive communications from the eNB. Such an RRC_CONNECTED UE would continue to monitor paging for ETWS and/or system information change notifications, and this would occur during a non-sleep portion of the DRX cycle. However, a UE that has neither received nor transmitted traffic for a while would be expected to be moved to RRC_IDLE (where the UE also has to monitor paging to determine if the network wishes to initiate contact with the UE) since this is a lower energy-consuming state than is RRC_CONNECTED (even with an extended DRX cycle configured).